Electron-tube circuit



June 24, 1930; L. A. GEBHARD 1,766,033

ELECTRON TUBE CIRCUIT Filed March 26, 1927 2 sheets-sheet 1 k' aa INVENTOR.

ATTORNEY June 24, 1930. L. A. 'GEBHARD 8 ELECTRON TUBE CIRCUIT Filed March 26, 1927 ZSheets-Sheet 2 I INVENTOR. 441 0146914. 5955474,

, ATTORNEY V affecting Patented June 24,1930" UNI ED *STATES Louis A. GEBHARnoFwAsHINGroN, nrsrnioriorooruivnam, As'sIGNoRiBY MESNE ASSIGNMENTS, FORNIA. y

' Emerson-T BE cmcurrf Application filed March 26, 1927. Serial No. 178,791.

My invention relates broadly. to' high frequency signal transmission circuits and more particularly tov a system' for controlling the filament circuits of theelectron tubes of the transmission circuits. I

One of the objects of my invention is'to provide a system for supplying the filament heating current to thefilament electrodes of the tubesof a high frequency transmitter in such manner-that the-efiective life of the filament electrodes may be prolonged.

Another object of my. invention is to provide a protective system for the filament elec-. trodes ofa plurality of high power tubes in a transmission systemxby which sudden; excess current is prevented frominjuriously the filament electrodes Still another object of my invention is to: provide a time delay circuit for energizing the filament electrodes of aplurality ofel'ec tron tubes whereby the filament temperature is automaticallyincreased from a prede'ter-, mined normal valueto an electron emitting temperature. for running condition for preserving the life of the electron tubes.

' stood from the specificationhereinafter fol-o 9 My invention will be. more fully underlowing by reference to the accompanying drawings wherein Fig.1 1 diagrammatically.

illustrates invention in association with a high frequency electron tube. transmiss on system wherethe cathode circuitsare energized from-direct current;and Eig. 2shows my invention applied to. an electron tube transmitter'where the tubes have their fila-. ments'supplied from an alternating current source. v V q My invention provides for the protection ofthe cathode circuits of high power, tubes wherein it is undesirable to havev a very high starting current in comparison to running taryinterruptions inu se. This is the case in the vacuumtube filament circuit, parl ticularly in high power'tubes. The filaments generally have a comparatively lowjresistance at normal atmospheric. temperatures,

the electron emitting properties of the resistance increasing to an efiective' high value at operating temperature. When: the voltageis'applied to the tube filament terminals th'ec'urrent will 'rise'to a high value unless there is a current limiting device interposed in circuit therewith-in accordance with the principles of my invention.

' It is desirable as matter ofeconomy tov reduce the temperature'of the vacuum tube filamentsto a moderate value without disconnecting the voltage entirely when the set is not actually sending out signals.v This must be done automatically at adefinite time after the operator releases the sending key. When the operator desires to use the setagain the TO FEDERAL TELEGRAPH oo vrr Y, A CORPORATION or CALL; i

temperature should rise to operatingvalue withthe first click of the key, as isaccomplished'in the circuit arrangement of myine vention.v

" My invention is illustrated' 'asapplied to for impressing high frequency signaling en.

ergy on antenna counterpoise'system 28 and 29. The cathodes ll 13 =and 14 are con nected through transformer. systems when the supply is alternating current as shown in Fig. 2 andwhen the supply is direct current. thefcathodes are parallel connected to the supply circuits as shown in Fig. 1.

111 Fig. Q'reference character 13 designates one-of the vacuum tubes, the filament 13 of which isconnected to. -secondary terminals.

10 and'12of a transformer 9, the-center tap 11 being grounded. The primary winding of transformer 9 isconneoted through a rheostat 8 and a resistance 6 to an alternatingjcun' rent. supplyline 7. 5 is a time limit relay so arranged that when Voltage is applied to its coil terminals 17, its contactsl8 close instantaneously and short circuit the resistance 6. v When the applied voltage is disconnected. aftime. delay device comessinto operation holding the contacts closed for a definite time limit after wliich they open and remove the short circuit firom resistance-6. The length of-time delay is adjustedto suit the particular conditions by proper setting of the parts, of the relay, the normal timebeing about I 20 source 24 .tooperate the relays. h

In normal; operation, before the set is started, the'operatorskey 23 is open.

there is no voltage on relay 2 the contacts '25 19 are open and therefore there is no voltage 2 n i i twenty seconds. Resistance 6 is of proper value to reducethe temperature of the fila-' ments tothe desired point. Rheostat 8 is of suificient resistance to .7 adjust the voltage at V terminals 10 and 12 to proper value when resistance 6 is shunted by contactslS.

. The voltagesupplying 'coil 17 is obtained 1 from source 1 through contacts 1910f relay V 2. Across these contacts is connected aspark reducing 'clrcult 'consistlng of "resistance" 3 and condenser 4 which is not absolutely essential to the operation of'the device but affords more rapid keying and lowers the liability of contacts sticking.

V 3 Contact 22 of relay 14 connects-to the grid or other circuit 16 of the vacuum'tube'13 and "controls its output; The coil 34 of relay 14 and the'coil of relay 2 are connected in se-' ries'or paralleland to line 15. This line in.- cludes the operators key 23 and apower Since 7 across coil '17 of relay 5, and therefore its contacts 18 areopen. Resistance (Sis-in the I circuit and limits the current in the tube 13 19 close.

' c 13' and a signal issent out.

when supply source 7 is closed. 7 When the operator first presses the key 23 both relays 3i and '2 are energized andcontacts 22 and Contact'19 i closes circuit to 17 which in ,tur-n'instantaneously closes contacts 18shun-ting out resistance G and allowing the current and therefore the temperature of filament of tube 13, to rise to operating value. Contacts 22controlthe output of tube Ifthe operator now' lifts his key 23- for spacing or other 7 reason, contacts 18 are held closed and the filament temperature of tube 13 is kept at normal operating value by the time limit device of relay 5 which maybe a bellows, oil dash potorother device. of similar nature; N If the operators key 23 'remains open for a longer'period than thetime limit is set for,

the contacts 18 open c and I the filament temperature fa-lls to 'thep'oint determined by re- 5 The time delay sistance 6. 'When the operator again closes his key the operationias above described re-e peats; V c i r I V V feature as employed in the transmission circuit is a'very valuableone;

The life of a tube depends upon the temperatureiof the filament. Infact at normal operating temperature'the life is lengthened 7 considerably with a very slight drop in tem'-' perature. The high currents in starting due to" the low resistance of thefilament tend to injurethe' tube if not to cause 'itsentire de structionf The device described corrects as faras possible'these difficulties.

lEtSllOUlClbQ noted that the source of tube V '7 lighting 7 maybe direct current 'instead of alternating current (Fig. 1) in -which case transformer 9 may be eliminated If elimi-- be someo'ther device than a vacuum tube. 'lnithe direct current system illustrated in'Fig. 1 the cathodes 11 13 andjl i are .parallel connected and may be independentnatedalternating or direct current may be used. It should also be noted that 13 may 1y controlled through the adjustable resistors 8 and to thedirect current supply line in-:

dicated at 30 in Fig; 1; f The time delay apparatus heretofore described i'niconne'ction 'with the. alternating supply currentsystem is similarly employed in the direct current supply system,v so that when the operators key 23 remains openfor periods longer than the predetermined time limit the contacts open and the filament temperature falls to a value determined by the resistance 1 .6, the

filaments being always ready .to be brought; 7

up to operating temperature upon the closing of the operators sendingkey; V 5

The invention described herein has been found to be extremely-practical in its operation on long distance electron tubet'ransmission circuits where transmission has been effected for distances of5,000 miles.

While I have described-preferred embodiments of the invention, .I desire that it be understood that modifications maybe made and that no limitations upon IHYdDVGIltlOH are intendedother than are imposed bythe V desire'to secure 7 a grid and a plate, a modulation circuit,,a.

keying circuit for'cont'rolling said modulat1on'c1rcu1t,a cathode supply source,a cathode supply circuit connected 'to'said'source and connections between said'keying circuit 7 and said catliode supply' circuit whereby thej supply of-cathode heating {energy may be modified at a predeterminedtime interval afterthe opening of said keymg circuit.

2. An electron tube transmission system comprising a plurality of electron} tubes, acathode; supply source; a cathodefsupply" circuit for said electron tubes {connected to said source, a keying circuit for controlling the operation of said electron tubes,a relay 1 clrcult, contacts disposedin'saldcathode'sup ply circuit, and controlled by said relay recircult, connections between said u relay circuit .1

andsaid keyingcircuit whereby said keying ClICllli? directly and automatically controls circuit from said cathode supply source at predeterminedtime-interval after the openthe, supply of energy to said cathode supply ing of said keying circuit bycontrolling said,

relay circuit and opening and closing said 1 contacts.

3. An electron tubetransmitter"compris ing a plurality of electron tube circuits, a

keying'circuit connected with said electron tubes, a cathode supply source, a cathode supply circuit extending between said source and the'cathodes of said electron tubes, and connections between said keying circuit and said cathode supply circuit for reducing the energy impressed upon said cathode supply comprising a plurality of electron tubes, a

cathode for each ofsaid tubes, a cathode heating circuit for said electron tubes,'a power supply source connected with said heating circuit, a circuit controller interposed between said power supply source and said cathode heating circuit and operative to maintain the cathodes of sai l tubes at an electron-emit-' ting temperature; or in a condition below an electron-emitting temperature, a keying circuit, and-means interposed in said keying circuit for determining the operation of said circuit controller in said cathode heating circuit in accordance with the operation oi?- said keying circuit'and changing said cathodes from an electron-em1ttingcondltion to a condltion'below an electron-em tt ng temperature.

6. An electron tube transmission system including a plurality otelectron tubes, a cathode for each of said tubes, a cathode heat ing circuit for said electrontubes, a power source, connected to said heating circuit, a circuit controller comprising a make and break contactor in shunt with'a resistor interposed between said power supply source and said cathode heating circuit, a relay winding controlling said make and break contactor for maintaining the cathodes atan electron emitting temperature or at a temperature be low an electron-emitting condition dependent upon the effect of said resistor in said cathode emitting circuit, a keying circuit, and

' means in said keying circuit for energizing said relay winding in timed relation to the transmission of signals.

7 An electron tube transmission system including an electron tube circuit having a cathode and a cathode heating circuit, a circuit controller interposed in*said. cathode heatingcircuit including a resistor and a make andbreak contactor in shunt thereto,

a keying circuit connected tosaid electron tube circuit, and means controlled saia' keying circuit for "operating said make and breakcontactor'for rendering saidresistor elii'ectiv'e or ineffective in said cathodeheating 3 circuit for controlling the condition of said cathode heating circuit and maintaining said Y cathode in an electron-emitting conditioner below an electron-emitting condition.

g 8. An electron tube: transmission system comprising-a plurality ofelectron tubes, a cathode for each of said tubes, cathode-heating. circuits for said'electron tubes, a power 1 source connected with said cathode heating circuits, .a resistance for limiting the energy supplied to said cathode heatingcircuits, Ia keying circuit, means controlled by said keying, circuit for shunting said resistan'ce, said meansbeing actuated in timed relation'to the operation of saidkeying circuitfor changing the eiiective-wvalue, of the resistancerin said cathode heat ng clrcu ts and maintaining said cathodes in an electron-em1tt1ng condition or at a temperature belowan electron-en'iitting condition; 4

An. electron tube transmission system comprising a plurality'ofelectron tube circuits, a cathode foreach of said tubes,a oathode supp-lysource, cathode heating circuits for said electron'tubecircuits connected to said cathode supply source,resistance means interposed insaid cathode heating circuits,

a keying circuit, altime controlled relay governedv by saidkeyingcircuit and connected to control the operation ofa circuit inshunt with said resistance meansin timed relation-- to the operation of said keying circuit for chan ing the effective value of the resistance in said said cathodes in an electron-emitting condition or at-a temperature below-electron emitting condition. I

10, An electron tube transmission system comprising a plurality of electron tubes, a cathode for each of said tubes, cathode heating circuits for said electron tubes, a power source connected with said heating circuits, a

cathode heat-circuits and maintaining resistance member, a relay circuit for interposing said res stance member between sald p power source and'said cathode heating circuits or shunting said resistance member with respect thereto whereby sa d cathodes may be maintained in an electron-emitting condi-.-

tion or in a condition immediately below an electron-emitting temperature, a'keying circuit and a time controlled relay controlled by said keying circuit for efiecting the operation of said aforesaid relay circuit 7 for placing said cathode heating circuit in either one of c,

said conditions in accordance with the operation of the keying circuit, 7 r

11. An electron tube transmission system 1 comprising a plurality of electron tubes 'having cathode heating circuits, a power supply circuit for energizing said cathode heating circuit, a resistance member interposed in said power supply circuit, a relay'haying its i contacts arranged in parallel with said resistance member, a keying circuit, a time controlled relay controlled by said keying circuit, said time controlled relay being far:

ranged to govern the operation ofsaid contacts for shunting said resistance member during signaling periods and maintaining an short circuit across said resistance member for a predetermlned t me lnterval after each signaling'period for maintaining said oath-V v ode heatlng CIICLlllZS in'a cond tion of maXr- V mum energization and decreasing the enercathodeiheating-circuit, a set of contacts con- I gization of said cathode heating circuits after the expiration of said predetermined time interval." i v '12. An electron tube transmission system v comprising a plurality of electron-tubes,a

cathode heating circuit for said electron tubes, a power source connected With said cathode heatlngcircult, a resistor interposed in serles between'saidpower source and said nected across said resistor, a solenoid for controlling the opening and closing 'of the said set of contacts, a control circuit including said solenoid, a keying circuit, a time controlled relay included insaid control circuit for controlling the conditionofsaid control circuit for effecting the opening or closing of saidset of contacts in timed relation to the operation of said keying circuit for changing the conditionof energization of said oathode heating circuit. r

I LQUIS'A, GEB HARD. 

